Josh and Susan Powell
Chris Detrick/The Salt Lake Tribune/AP; Amber Hardman/AP
02/10/2012 AT 07:00 PM EST
A comforter found in Josh Powell's storage unit after he killed himself and his two boys contained a stain that tested positive for blood, court documents revealed Friday.
At the time of his death, Powell was considered a person of interest in the 2009 disappearance
and presumed death of his wife Susan when they resided in Utah. Authorities now say his father, jailed on child pornography charges, is also a person of interest.
The gray-blue comforter was seized from a Sumner, Wash., unit on Tuesday, two days after Powell, 36, blew up
his Tacoma, Wash.,-area house with him and his sons Charlie, 7, and Braden, 5, inside.
A presumptive test conducted in the field came up positive for blood, and additional testing in the lab will be conducted, the Associated Press reports.
"Field tests are not infallible," says Pierce County, Wash., Prosecutor Mark Linquist, according to AP.